1. Field of the Invention
The present invention relates to using a licensed shared access spectrum in a radio access network where signal propagation is unknown. In particular, the invention relates to controlling a wireless transmission of a network element of a radio access network where signal propagation is unknown.
2. Related Background Art
The following meanings for the abbreviations used in this specification apply:
3GPP Third Generation Partnership Project
ALC ASA/LSA Control
ASA Authorized Shared Access
BS Base Station
BSud Base Station Uncoordinated Deployment
C Cell
CN Core Network
DSL Digital Subscriber Line
GNSS Global Navigation Satellite System
GPS Global Positioning System
HeMS HeNB Management System
HeNB Home eNodeB
IP Internet Protocol
LAN Local Area Network
LI Location Information
LSA Licensed Shared Access
LTE Long Term Evolution
LV Location Verification
OAM Operation Administration & Maintenance
OMS OAM System
RF Radio Frequency
RSPG Radio Spectrum Policy Group
UE User Equipment
In an effort to extend capacity for broadband wireless access to a communications network system, base stations (Macro, Pico and Femto) have been introduced, which are enabled to use a licensed shared access spectrum, e.g. ASA (authorized shared access) spectrum also known as LSA (licensed shared access) spectrum. ASA/LSA is a third and complementary way of authorising spectrum, in addition to licensed and license-exempt (unlicensed) spectrum. ASA/LSA spectrum is typically owned by an incumbent (primary user) who allows other licensed operators (secondary user) to use this spectrum for their purpose. ASA/LSA allows support of different operators by using separated ASA/LSA resources. Each ASA/LSA resource is defined by a spectrum part and a corresponding time interval and location where this spectrum part is used.
In mobile networks spectrum utilization and allocation is performed via static configurations based on network planning data of a mobile network operator (MNO). With the introduction of ASA/LSA it is not longer possible to stay with these static configurations because ASA/LSA spectrum needs to be evacuated according to predefined terms and conditions if requested by the incumbent (primary user). The principle of >>my spectrum—my usage<< will not hold any longer. In other words the well known static spectrum allocation methods need to be complemented which leads to a paradigm change in mobile communication industry. In addition to the traditional exclusive spectrum assignment there is now also a new method where (in some regions) certain parts of the spectrum may no longer be exclusively assigned to a single operator but jointly assigned to several operators with the obligation to use it collectively.
As mentioned above a main characteristic of ASA/LSA is that the incumbent may reserve an ASA/LSA resource for own usage. Such reservations could be defined by static rules (e.g. a defined zone and/or time where the spectrum is used by the incumbent) or dynamic rules (e.g. evacuation of spectrum on request for emergency situations). In both cases zones where spectrum use under ASA/LSA is not allowed are defined by geographical area, time and transmitter/receiver characteristics. Additionally the evacuation lead time, this is the time between initializing the request to free up the ASA/LSA spectrum zone and the finalization of the spectrum evacuation, may be defined as another input parameter to the operator. The operator has to perform appropriate measures in the network, e.g. re-configurations or switch off ASA/LSA spectrum of specific base stations without violating the evacuation lead time in case of spectrum resource reservation actions triggered by the incumbent. Typically such measures are easy to realise because the location and behaviour of each operator base station and the reservation zones are known and can be used in a planning process to get the information needed to perform reservation actions.
FIG. 1 shows such a scenario with four 3 sector base stations BS1, BS2, BS3 and BS4 covering a defined ASA/LSA license zone, where each sector defines an independent cell C1, C2, . . . C12. Inside the ASA/LSA license zone the incumbent has defined a reservation zone which needs to be evacuated on request.
The operator uses the input to determine the affected cells C8, C9 and C10 and derives the measures for evacuation, e.g. switch off ASA/LSA spectrum for C8 and C9 and reconfigure C10 to reduce cell size, as illustrated in FIG. 2.
In case of unknown signal propagation of base stations, the described process does not work because e.g. the location of each base station is unknown and may even change several times in case of small base stations (Pico and Femto). This makes it nearly impossible to prepare a reliable measure to guarantee that a base station does not interfere with a defined ASA/LSA reservation zone which is shown as hatched area in FIGS. 1 and 2.
Unknown signal propagation due to uncoordinated deployment of base stations and unknown configuration of the base stations is an important issue at least for Femto, Pico and LTE-LAN installations, because all operate in licensed spectrum. When such types of base stations are used as senders/transmitters the operator has to guarantee that they are operated according to their license, i.e. using the licensed spectrum in the licensed area. Compared with Femto there is until today no method standardized to determine the exact location of a base station in case of uncoordinated deployment of base stations, but even for Femto the methods do not fulfill the requirements for ASA/LSA usage.
Femto is often used in home environments where the subscriber chooses the exact location of the base station. Based on the fact that Femto base stations are designed for easy installation and operation it may happen that a subscriber tries to use the Femto in a location where the operator has no license. To help operators to detect and prevent such situations 3GPP has introduced a process to verify the location of a Femto base station before allowing the base station to transmit. Following methods are available for location verification (LV):                neighbourhood information (Femto base station scans neighbourhood and collects data from other base stations);        GNSS location information (Femto base station determines location coordinates based on GPS); and        broadband connection information (Femto base station provides IP address and/or other broadband credentials).        
It is allowed to use one method, or any combination of two methods, or all three methods. While the mentioned methods fit to a number of situations (e.g. GPS for Femto outdoor installations) there is also a high number of scenarios where the mentioned methods deliver only coarse location information or even none of these methods are available. The reason is that most Femto access points in residential deployments are installed indoors in areas where no macro coverage is available. Indoors does not allow to receive GPS signals and the broadband credentials are also not available because the Femto base station is in nearly all cases connected to a home router (DSL router) which provides a private IP address to the Femto base station (public IP address sharing).
As a result none of the defined methods for location verification fits to the ASA/LSA use cases.